a = {'zero': 0 , 'one': 1, 'two': 2, 'three': 3, 'four': 4, 'five': 5, 'six': 6, 'seven': 7, 'eight': 8, 'nine': 9}
try:
    n = input()
    b = n.split(" ")
    m = ""
    c = []
    for i in b:
        c.append(str(a[i]))
    z = "".join(c)
    if 100<=int(z)<=1000:
        def is_prime(n):
            if not n % 2:
                return n == 2
            d = 3
            while d * d <= n and n % d:
                d += 2
            return d * d > n
        num = int(z)
        tmp = abs(num - 2)
        res = 2
        k = 3
        while True:
            if is_prime(k):
                t = abs(num - k)
                if t < tmp:
                    tmp = t
                    res = k
                else:
                    print(res)
                    break
            k += 2
    else:
        print("Wrong input")
except Exception:
    print("Wrong input")
